The chilling threat comes as tensions between the two sides reach boiling point a year after Washington abandoned an agreement between Iran and world powers to curb its nuclear programme in exchange for the lifting of international financial sanctions. Fears of conflict prompted a rare intervention from Japanese Prime Minister Shinzo Abe who has flown to Iran for talks with leaders aimed at reducing tensions in the pressure-cooker region.

Japan is in a unique position to act as a mediator as the US ally has also maintained close ties with Iran.

Mr Abe warned of unintended clashes in the crisis-torn Middle East after meeting Iranian President Hassan Rouhani.

Speaking after talks with Ayatollah Khamenei today he said: “Supreme Leader Khamenei made a comment that the country will not and should not make, hold or use nuclear weapons, and that it has no such intentions.

“Today, I met Supreme Leader Khamenei and heard his belief in peace. I regard this highly as a major progress toward this region’s peace and stability.”

Japan is in a unique position to act as a mediator as the US ally has also maintained close ties with Iran.

But any hopes Mr Abe could act as a go-between appeared to falter when the Ayatollah dismissed US President Donald Trump of as “not worthy”.

He told the Japanese leader: “I don’t consider Trump as a person worthy of exchanging messages with.